Interesting question. I'm sorry that I do not have an answer for you but you have brought up a good point. Corals and especially SPS need a fair amount of space to grow. To often we jam our system with scores of frags merely inches from each other. I advocate the proper spacing of corals in order to allow them to grow correctly.
Nature is a funny thing, as it has programed all creatures for survival. I'm guessing that your question would almost be akin to asking what instinct in animals is. Here is what I could find concerning instinct:
"The fixed action patterns are unlearned and inherited. The stimuli can be variable due to imprinting in a sensitive period or also genetically fixed. Examples of instinctual fixed action patterns can be observed in the behavior of animals, which perform various activities (sometimes complex) that are not based upon prior experience, such as reproduction, and feeding among insects. Sea turtles, hatched on a beach, automatically move toward the ocean, and honeybees communicate by dance the direction of a food source, all without formal instruction. Other examples include animal fighting, animal courtship behavior, internal escape functions, and building of nests. Another term for the same concept is innate behavior. Instinctual actions - in contrast to actions based on learning which are served by memory and which provide individually stored successful reactions built upon experience - have no learning curve, they are hard-wired and ready to use without learning. Some instinctual behaviors depend on maturational processes to appear.
Biological predispositions are innate biologically vectored behaviors that can be easily learned. For example in one hour, a baby colt can learn to stand, walk, glide, skip, hop and run. A biological predisposition may also mean that a person, because of his/her genetic makeup, is more prone to certain conditions or disease. Learning is required to fine tune the neurological wiring reflex like behavior. True reflexes can be distinguished from instincts by their seat in the nervous system; reflexes are controlled by spinal or other peripheral ganglia, but instincts are the province of the brain. In a situation when two instincts contradict each other, an animal may resort to a displacement activity".
I hope this helps. :) If anyone else has a proper explanation please contribute.
Sonny
